1. Field of the Invention
The present invention relates generally to aerodynamic wings or aerofoils for use with boats and, more particularly, to aerodynamic wings to reduce drag on a boat hull by providing a lifting force near the variable center of gravity of the boat.
2. Description of the Prior Art
In recent years, various means have been developed for raising the hull of a boat in the water to reduce the drag, or retarding force, acting on the hull as the boat moves through the water.
One means for providing this lifting force is through use of hydrofoils. Several hydrofoils can be mounted on struts below the boat to provide a lifting force on the boat that increases as the speed of the boat increases. As the boat rises out of the water, the retarding forces acting on the hull are greatly reduced. For the same amount of energy applied to the propeller, a substantial increase in boat speed is achieved. Although this technique is successful, it does have limitations. For instance, the draft of the boat is necessarily deeper when the boat is going too slow to utilize the hydrofoils beneath the boat. The hydrofoils also affect the steering of the boat at low speeds which creates problems for docking, unloading via crane when water currents affect boat position, and other slow speed maneuvers. Furthermore, the lifting force is generally entirely dependent on boat speed because the hydrofoils generally have a fixed pitch, or angle, relative to the water. Depending on sea conditions, it may be desirable to provide only a certain amount of lift to the hull. However, because the hydrofoil generally has no adjustment for pitch, the only way this can be done is by driving the boat at a specific speed which may not always be a optimum speed for the particular conditions.
On the other hand, the use of an aerodynamic wing above the boat has generally not been successful because, for at least one reason, the placement of such a wing has been so problematical that it has not been thought possible or useful to attempt to realize the benefits of any lifting force that such a wing would provide. The problem encountered is that the lifting force of the wing often causes the boat to assume an awkward pitch with the stern or bow too high. When the boat assumes such an awkward position any gains in efficiency obtained by lifting the hull are lost due to the added resistance the hull may acquire because of its awkward pitch.
Consequently, a need exists for improvements in using aerodynamic wings on boats which will result in greater efficiency and dependability of operation at reduced levels of energy consumption.